Russian troops in the eastern extremities of Siberia derive some enjoyment during moments of idleness from tuning to Radio Nome, a US station across the water in Alaska. Apparently they like the music.

But on 30 August the most pertinent content of Radio Nome was, for the Russians, a message in their own language from one Baron Arnaud de Rosnay telling them that he was on his way over. A solitary Frenchman was going to cross the Bering Strait by sailboard and was planning to land, uninvited, in one of their most closely guarded military zones.

De Rosnay comes from a family that owns sugar estates in Mauritius. His marriage (since dissolved) to Sir James Goldsmith’s daughter, Isabel, was an important event in the young jet-setters’ calendar of 1973. For fifteen years de Rosnay has been a photographer. ‘But now,’ he says, ‘I want to make a movie.’ He has an idea in mind – ‘an inner-vision spectacle’ is how he describes it. ‘It is basically about nature and sport. It’s a new style of movie.’

‘Before I began to produce it,’ he explains, ‘I wanted my name to be associated with nature and sport.’ So he planned two expeditions that tested his expertise at sport and knowledge of the natural environment. The first was in March, when he attempted to cross the Sahara from Morocco to Senegal by sailing across the desert on a four-wheeled land yacht. Only part of the journey was accomplished: the Baron was turned back by Moroccan authorities because of the war with the Polisario. On his return he decided he would cross the Bering Strait – the narrow stretch of water (60 miles at one point) that separates the U.S. – the north-west coast of Alaska – from Russia. He would go by sailboard. His original plan was to travel by helicopter from Alaska to Russia with his sailboard and then, taking advantage of the prevailing winds, sail eastwards.

The Baron, who is not without connections in the right places, enlisted the co-operation of the Americans. Then he approached the Russian Embassy in Paris. ‘I really had a lot of help at first,’ he says. ‘I had a long meeting with the Ambassador and he raised such questions as would it be an American helicopter landing on Russian soil, or a Russian helicopter landing in America.’ However, the strait is closed by ice from November to June and the Russians later wrote to de Rosnay telling him that they would not be able to make the arrangements in time. ‘But never did they say they wouldn’t allow me to do it’; and for de Rosnay that was enough, permission by default.

He set off for the U.S. determined to tackle the journey – but in the opposite direction. He arrived to find that American support for the project had suddenly disintegrated in the absence of Russian permission. ‘They didn’t want to be part of what they considered to be an illegal operation – so they cancelled any help, including coastguard helicopter support. ABC Television, concerned about its position at the Moscow Olympics, withdrew its coverage. No company would hire me a plane to reach the starting point. I had to get one privately. Everybody cancelled. But that made me even more determined to go ahead with it.’

Eventually, at 10.15 one blustery morning, watched by a small group of friends and helpers, he set off. A compass was fixed on the arm of his wetsuit and in a bag on his harness was his emergency equipment – it included small signalling fl ares, vitamin pills and a knife. In a waterproof bag fixed to the board was a change of clothing, a camera, his passport, a cutting from Pravda about his Sahara crossing, the letter from the Russian Embassy, some chocolate and $500 (about £250) in cash. The message he had recorded for Radio Nome was broadcast half an hour after his departure. ‘We knew the Russians liked to listen to the station,’ he says.

For four months de Rosnay had been studying the waters of the strait. He had learnt that the mountains on either side channelled the wind in such a way that it tended to be stronger at the two sides than in the middle. When he started it was quite light and all went well until he was about halfway across: then the wind dropped almost completely. He spent an awkward two hours trying to maintain his position in the choppy water against the current. In the afternoon the wind changed direction and increased sharply.

De Rosnay had begun to tire and, besides, he was getting extremely cold. During the ten days of training before he set off he had tried to use his gloves as little as possible because their waterproof rigidity made holding the wishbone (the boom of the craft) more of a strain. However, now that his hands were cold, he reached for his gloves – only to discover he had lost them. His fingertips remained numb for weeks afterwards as a result.

After he had been going for six hours the wind was blowing strongly and he began sailing fast – about 20mph. ‘It was like waterskiing!’ It was then that he first saw the Russian warship. It was about three miles away. It followed him for two hours, until he reached the Russian shore. He landed on a beach under some cliffs. ‘The sea was really turbulent here and I fell off several times before I came ashore. The water was two degrees Centigrade – colder than on the American side. It was a big shock. When I landed I was freezing – I did some gymnastic exercises just to keep warm. I ate some chocolate and took some pictures: that was important because it proved I had landed,’ he says.

Then de Rosnay saw a launch from the Russian ship coming towards him. ‘I didn’t know what their reaction was going to be. I decided to go out and meet them.’

The crossing had taken eight hours, and he was now extremely tired. He kept falling off, and when the launch reached him he was in the water, exhausted, clinging on to the sailboard. He was hauled aboard the launch and a Russian officer who spoke excellent English gave him a fur coat, bread and pâté and cigarettes. ‘They were very nice to me. They were sailors and they knew what it meant to cross that stretch of water.’

De Rosnay was taken ashore, where other offi cers were waiting near a helicopter. ‘They asked me, “Do you realise that you have entered Russia without authorisation?” and I said, “Well, you know, I’m a bit like a seagull – I came with the wind, I was going back with the wind.”’ He was later to be proved wrong.

De Rosnay was taken to a town called Uelen and entertained to a meal by several officers. The next day, after being shown around, he was told that in view of his achievement the authorities considered him a guest of honour in transit, and he was to be taken to Moscow and thence to Paris. He tactfully pointed out that he had friends waiting for him across the water in Alaska, but the Russian plan was politely but firmly adhered to.

The origins of this insistence may well have lain in an awkward scene at Kennedy Airport in New York three days earlier when the Americans had held up the departure of Ludmilla Vlasova, wife of the Bolshoi Ballet defector Alexander Godunov.

Although in no mood to deal with the Americans over de Rosnay, the Russians must have been charmed by the endeavours of their uninvited guest, a playboy from the Western world who zigzagged through their defences on a windblown plank as easily as a butterfly might pass through barbed wire.

This extract appears in Bon Voyage!: The Telegraph Book of River and Sea Journeys, edited by Michael Kerr (Aurum Press). It can be ordered through Telegraph Books (0844 871 1514; books.telegraph.co.uk) at £20 plus £1.25 p & p

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